The invention relates to an electrical circuit for driving a load.
In as far as electric or electromechanical systems require a measurement of current, such measurement is usually performed in that the current to be measured is guided via a shunt resistor. The resultant voltage drop can be detected by measurement technology and, provided that the resistance value is known, be converted into a current value. Thus, what is required is an accurate knowledge of the resistance value of the shunt resistor. However, shunt resistors are cost-intensive and are subjected to relative large manufacturing tolerances. Further, it is often necessary to solve problems in the assembly process. Finally, the resistance value of a shunt resistor is dependant on the temperature.
For current measurement in an electric or electromechanical system, it is thus of advantage if one can make use of the voltage drop across a component existing in the system. In this regard, however, it is to be considered that the resistance value of such a component may lie within a per se known range of resistance values. Under this aspect, it is thus required to determine the resistance value of the component prior to the start of the intended use of the electric or electromechanical system, wherein the only known parameter is to be seen in that the possible minimum value and the possible maximum value of the resistance of the respective electrical component are known.
Thus, it is an object of the invention to provide an electrical circuit comprising a device for determining the resistance value of a transistor of this circuit which only the maximum possible resistance value and the minimum possible resistance value are known.